AN offshore union has cancelled a protest targeting the operator of a helicopter which crashed into the North Sea, killing four people.

The National Union of Rail, Maritime and Transport Workers (RMT) said it had secured a "massive breakthrough" on access to the workforce on platforms and at heliports.

It had planned to protest near the Aberdeen heliport of CHC, the operator of the Super Puma helicopter that came down off the southern tip of Shetland on Friday night.

The crash was the fifth incident involving Super Pumas in the North Sea since 2009.

A rally will instead be staged outside the union's headquarters in the city's Crown Street calling for safety improvements.

The stricken Super Puma. (Image: Shetland News)

General secretary Bob Crow said that Oil and Gas UK had met the union's demand of guaranteed access to offshore workers.

He said: "This means we can speak to our workers and find out what their concerns are and relay them back. It gives them a voice.

"The rally will let people offshore know that we are doing everything possible to try and secure safety for them and their families."

Relatives of those killed as a result of offshore safety failings are expected to attend the event at 11am tomorrow.

A search for the aircraft's black box data recorder, which was in the helicopter's tail section, is being carried out by salvage experts at the site of the crash using specialist sonar equipment.

There were 16 passengers and two crew on the Super Puma AS332 L2 travelling from the Borgsten Dolphin support vessel when it crashed into the sea, killing three men and one woman.

The victims were named as Duncan Munro, 46, from Bishop Auckland, County Durham; George Allison, 57, from Winchester, Hampshire; Sarah Darnley, 45, from Elgin, Moray; and 59-year-old Gary McCrossan, from Inverness.

Three of the bodies from the crash arrived in Aberdeen by ferry on Monday morning and the fourth reached the city, also by ferry, by 8am today.

It emerged today that workers on the Borgsten Dolphin were given a briefing by senior staff from CHC and oil giant Total on the safety of Super Pumas on August 8.

During the talk, CHC chief pilot Will Hanekom and Total head of logistics Christophe Barbier sought to reassure staff concerned about the safety of the EC225 helicopter model, according to the Press and Journal newspaper.

In a recording of the briefing obtained by the paper, a Total manager is reported to have told staff not to work offshore if they could not live with the risk of flying in helicopters.

Workers were also told by a pilot that "at some point we have to put our big-boy pants on", the paper reported.

A Total spokesman said the remarks had been made during one of a series of offshore visits ahead of the re-introduction into service of the EC225 helicopter.

He said: "We wanted to explain to the workforce the comprehensive package of new safety features the authorities and the helicopter operators had introduced, and to listen to their views and any concerns.

"These briefings related exclusively to the EC225 model helicopter, which is a completely separate model to the one involved in last week's tragic accident."

A spokeswoman for CHC said the pilot's comments had been taken out of context.

"If people heard the whole recording they would understand this pilot was trying to get his message across as a fellow North Sea worker and not a corporate spokesperson," she said.

"This was his genuine, personal endorsement of the aircraft. He was demonstrating his confidence in the EC225. He acknowledged the risks facing them all in getting to, working on and getting home from rigs. He spoke about his family and how he wouldn't risk his own wellbeing - and neither should they."

CHC has temporarily held all flights of the three types of Super Puma helicopter that it operates - the L, L2 and EC225.

It follows a recommendation by the offshore industry's Helicopter Safety Steering Group (HSSG) which urged the precautionary measure until there is "sufficient factual information" to resume flights.

It is hoped information on the flight recorder, once traced, will help establish what caused the crash.

The wreckage of the helicopter is due to be transported to a mainland port on the Bibby Polaris salvage vessel.

Total has chartered boats to transport workers to offshore platforms following the crash.

Four vessels are being co-ordinated to operate between three oil producing platforms and other offshore drilling facilities in the North Sea while Super Puma helicopter flights are suspended.

There have been five North Sea incidents involving Super Pumas since 2009. In April that year an AS332 L2, operated by Bond, went down north-east of Peterhead on its return from a BP platform, killing all 14 passengers and two crew on board.

The other three ditchings involved the EC225 model which saw flights temporarily suspended. CHC returned the model to commercial service only earlier this month.

An investigation by the Air Accidents Investigation Branch found that two of the incidents were the result of gearbox failure and new advice on checks for the EC225 were issued as a result.

A fatal accident inquiry is expected to be held into the 2009 fatal AS332 L2 crash in Aberdeen next year.